Batman advanced is a new approach to wireless networking which does no longer
operate on the IP basis. Unlike the batman daemon, which exchanges information
using UDP packets and sets routing tables, batman-advanced operates on ISO/OSI
Layer 2 only and uses and routes (or better: bridges) Ethernet Frames. It
emulates a virtual network switch of all nodes participating. Therefore all
nodes appear to be link local, thus all higher operating protocols won’t be
affected by any changes within the network. You can run almost any protocol
above batman advanced, prominent examples are: IPv4, IPv6, DHCP, IPX.

Batman advanced was implemented as a Linux kernel driver to reduce the overhead
to a minimum. It does not depend on any (other) network driver, and can be used
on wifi as well as ethernet lan, vpn, etc ... (anything with ethernet-style
layer 2).

To make use of your newly created mesh, batman advanced provides a new
interface “bat0” which you should use from this point on. All interfaces added
to batman advanced are not relevant any longer because batman handles them for
you. Basically, one “hands over” the data by using the batman interface and
batman will make sure it reaches its destination.

The “bat0” interface can be used like any other regular interface. It needs an
IP address which can be either statically configured or dynamically (by using
DHCP or similar services):

All error messages, warnings and information messages are sent to the kernel
log. Depending on your operating system distribution this can be read in one of
a number of ways. Try using the commands: dmesg, logread, or looking in
the files /var/log/kern.log or /var/log/syslog. All batman-adv messages
are prefixed with “batman-adv:” So to see just these messages try:

$ dmesg | grep batman-adv

When investigating problems with your mesh network, it is sometimes necessary to
see more detail debug messages. This must be enabled when compiling the
batman-adv module. When building batman-adv as part of kernel, use “make
menuconfig” and enable the option B.A.T.M.A.N.debugging
(CONFIG_BATMAN_ADV_DEBUG=y).

Those additional debug messages can be accessed using the perf infrastructure:

$ trace-cmd stream -e batadv:batadv_dbg

The additional debug output is by default disabled. It can be enabled during
run time:

$ batctl -m bat0 loglevel routes tt

will enable debug messages for when routes and translation table entries change.

Counters for different types of packets entering and leaving the batman-adv
module are available through ethtool:

As batman advanced operates on layer 2, all hosts participating in the virtual
switch are completely transparent for all protocols above layer 2. Therefore
the common diagnosis tools do not work as expected. To overcome these problems,
batctl was created. At the moment the batctl contains ping, traceroute, tcpdump
and interfaces to the kernel module settings.